The present invention relates generally to network communications systems, and more particularly, to a method and apparatus for transmitting and switching data packets operating under the principles of a first quality of service (e.g., SIMA technology) in a system designed to transmit and switch data packets operating under the principles of another quality of service (e.g., ATM technology).
Communication of digital content between remote computing systems is increasing at astronomical rates as networks continue to proliferate throughout the globe. A great majority of personal computers used in business and in educational institutions are connected to a network, and the importance of emerging network technologies continues to increase as the masses feverishly enter the domain of the Internet. Data, audio, graphics, motion video, and other multimedia content are all vying for transmission availability in an era of limited, yet improving, bandwidths.
Providers of network services, and of communications system infrastructure, are faced with a number of complex issues in providing necessary bandwidth and quality service. These issues include management of network capacity, prioritization and management of both real-time and non-real-time data traffic, and implementing fair billing schemes. One solution to many of these problems is the use of packet-based digital data transmissions having an associated xe2x80x9cquality of service,xe2x80x9d such as the transmission technology referred to as Asynchronous Transfer Mode (ATM). Those skilled in the art understand ATM to constitute a communications networking concept that, in theory, addresses many of the aforementioned concerns, such as by providing a capability to manage increases in network load, supporting both real-time and non-real-time applications, and offering, in certain circumstances, a guaranteed level of service quality.
A conventional ATM service architecture typically provides a number of predefined quality of service classes, often referred to as service categories. Each of the service categories includes a number of quality of service (QoS) parameters that define the nature of the respective service category. In other words, a specified service category provides performance to an ATM virtual connection (VCC or VPC) in a manner specified by a subset of the ATM performance parameters. The service categories defined in the ATM Forum specification reference hereinbelow include, for example, a constant bit rate (CBR) category, a real-time variable bit rate (rt-VBR) category, a non-real-time variable bit rate (nrt-VBR) category, an unspecified bit rate (UBR) category, and an available bit rate (ABR) category.
The constant bit rate service class is intended to support real-time applications that require a fixed quantity of bandwidth during the existence of the connection. A particular quality of service is negotiated to provide the CBR service, where the QoS parameters include characterization of the peak cell rate (PCR), the cell loss rate (CLR), the cell transfer delay (CTD), and the cell delay variation (CDV). Conventional ATM traffic management schemes guarantee that the user-contracted QoS is maintained in order to support, for example, real-time applications, such as circuit emulation and voice/video applications, which require tightly constrained delay variations.
The non-real-time VBR service class is intended to support non-real-time applications, where the resulting network traffic can be characterized as having frequent data bursts. Similarly, the real-time variable bit rate service category may be used to support xe2x80x9cburstyxe2x80x9d network traffic conditions. The rt-VBR service category differs from the nrt-VBR service category in that the former is intended to support real-time applications, such as voice and video applications. Both the real-time and non-real-time VBR service categories are characterized in terms of a peak cell rate (PCR), a sustainable cell rate (SCR), and a maximum burst size (MBS).
The unspecified bit rate (UBR) service category is often regarded as a xe2x80x9cbest effort service,xe2x80x9d in that it does not specify traffic-related service guarantees. As such, the UBR service category is intended to support non-real-time applications, including traditional computer communications applications such as file transfers and e-mail.
The available bit rate (ABR) service category provides for the allocation of available bandwidth to users by controlling the rate of traffic through use of a feedback mechanism. The feedback mechanism permits cell transmission rates to be varied in an effort to control or avoid traffic congestion, and to more effectively utilize available bandwidth. A resource management (RM) cell precedes the transmission of data cells, which is transmitted from source to destination and back to the source, in order to provide traffic information to the source.
Although the current ATM service architecture described above would appear to provide, at least at a conceptual level, viable solutions to the many problems facing the communications industry, ATM, as currently defined, requires implementation of a complex traffic management scheme in order meet the objectives articulated in the various ATM specifications and recommendations currently being considered. In order to effectively manage traffic flow in a network, conventional ATM traffic management schemes must assess a prodigious number of traffic condition indicators, including service class parameters, traffic parameters, quality of service parameters and the like. A non-exhaustive listing of such parameters and other ATM traffic management considerations is provided in ITU-T Recommendation I.371, entitled Traffic Control and Congestion Control in B-ISDN, and in Traffic Management Specification, version 4.0 (af-tm-0056.000, April 1996), published by the Technical Committee of the ATM Forum.
Notwithstanding the complexity of conventional ATM traffic management schemes, current ATM specifications and recommendations fail to adequately address the need of service providers for a methodology that provides for accurate and reliable charging of services utilized by user""s of the network. Even if one were to assume that a charging scheme that accounts for most or all of the currently defined ATM traffic management properties could be developed, such a scheme would necessarily be complex and would typically require administration by highly skilled operators. The high overhead and maintenance costs to support such a billing scheme would likely be passed on to the network provider and, ultimately, to the network user.
The present invention is applicable in a network service class which incorporates a priority-based quality of service. This service class, hereinafter referred to as the Simple Integrated Media Access (SIMA) service class, provides a network management architecture that is simple in concept and in its implementation, yet adequately addresses the quality of service requirements to support a variety of network services, including real-time and non-real-time services. It also provides for the implementation of a simple and effective charging capability that accounts for the use of network services.
However, the existing network infrastructure does not necessarily account for data transmissions utilizing the SIMA service class, which includes a priority-based quality of service. For example, existing ATM switches residing in network nodes are not configured to manage data traffic based on the packet priorities and allowable node priorities implemented in a SIMA service class, and the benefits associated with the SIMA service class are not recognized.
Accordingly, there is a need in the communications industry for a network management method and architecture that recognizes SIMA packets and accounts for the traffic management principles provided by a SIMA service class within a conventional, non-priority-based network infrastructure such as an ATM network system. The present invention provides a solution to these and other shortcomings of the prior art, and offers additional advantages over the prior art.
The present invention is directed to a system and method for communicating SIMA information elements over a non-SIMA network. The present invention can be used in connection with a conventional network switch, such as an ATM switch, such that the inclusion of SIMA traffic on the network is recognized as standard ATM traffic as far as the ATM switch is concerned. The present invention makes possible the multiplexing of SIMA traffic over ATM connections, while accommodating the quality of service principles that make SIMA a valuable service.
In accordance with one embodiment of the present invention, a method is provided for communicating first data packets having a first quality of service over a network system designed for communicating second data packets having a second quality of service. The network system comprises a plurality of network nodes, where each of the network nodes includes a network switch. The method includes switching the first data packets from each of a plurality of network switch input ports to a dedicated output port of the network switch. Network node congestion control is applied to the first data packets at the dedicated output port to selectively accept or discard the first data packets in accordance with their respective quality of service acceptance principles. Those of the first data packets that were accepted are multiplexed into one or more virtual paths having common output port destinations, and the virtual paths are input into a dedicated input port of the network switch. The virtual paths at the dedicated input port are switched to output port destinations of the network switch identified by the common output port destinations.
In accordance with another embodiment of the invention, a method of communicating Simple Integrated Media Access (SIMA) information elements over a conventional, non-SIMA network system is provided. The non-SIMA network system includes at least one network node having a network switch. The method includes reserving at least one virtual path from each input port of the network switch for transmitting the SIMA information elements into the network switch. The reserved virtual paths from each of the input ports are switched to a dedicated output port of the network switch. Network node congestion control is applied to the SIMA information elements in accordance with predefined SIMA priority principles. Virtual channels from each of the reserved virtual paths are multiplexed at the dedicated output port such that the virtual channels having common output port destinations are collectively bundled into distinct virtual path outputs. The distinct virtual path outputs are provided to a dedicated input port of the network switch, and are switched to their respective output ports of the network switch based on the common output port destinations.
In accordance with another aspect of the invention, a network system capable of communicating packet-based SIMA and non-SIMA information elements between two or more end units in the network system is provided. The network system includes a non-SIMA network switch for multiplexing and routing the packet-based information elements between switch input ports and switch output ports on the network switch based on an information element address. The network switch includes a dedicated output port coupled to at least one of the inputs ports through the network switch to receive the SIMA information elements, and includes a dedicated input port to receive filtered SIMA information elements. The network system further includes a switch extension module coupled to the dedicated output port to receive the SIMA information elements, and to the dedicated input port to provide the filtered SIMA information elements to the dedicated input port. The extension module includes a packet filtering module to generate the filtered SIMA information elements by applying SIMA congestion management principles to each of the received SIMA information elements. In this manner, SIMA information elements can be seamlessly switched using the non-SIMA network switch.